Method of reconditioning drill bits



Aug. 10, 1943. R. E. CALHOUN METHOD OF RECONDITIONING DRILL BITS Original Filed April 29, 1941 Gal/6E Low znvenl or' fess/M50 090m:

08/6/1764 6007003 .Dau. 0 51;"

Con/701m usage.

Patented Aug. 10, 1943 W I 2,326,521 I v I METHGD:OFRIEGONDITIONENGLSDRILL BITS Y Bambi E; Calhoun, Metaline Falls,Wash." o'riginar application April 29, 1941; Serial No.

890,947; Divided and this application Febru any 6, B i2,.SeriaE No. 4295758 4 Claims (Ollie- 10s)- This invention relates to improvementsin a methodof-reconditioningdrill-bits;

' It is well known by 'those who engage inthe constructionand"- maintenanoe of mine tunnels or in any onemtion' ofan engineeringnatureem: ploying the drilling of holes in theearth or rock for the purpose of blasting; that the-reconditiom ing of the worn or-dull'ed bits or the drills presentsa problem that in some respectehas-never been satisfactorily'selved; 1

With the adventofthe detaehable bit; which has largely replacedthe conventional steelof former use, the need for adequateand easily operated.- reconditioning mechanisnr has grown veryacute:

A; drill bit; which ordinarily has from two to four teeth or wings, when it'ieusedlbses height due to the dulling or flattening of the; cutting edges of the teeth. In addition, it also-leses s-i'ze in gaugedi'ameter due totlie underentnatureoi the end-era sharpenedibit tooth-to brevide'ada quate cl arance for the'rea-rward passage or dust and, the like from the cutting face of the hole being drilled.

The gauge cornersof" the bit are worn away and consequently the width of the bit'is materially reduced from its original site. In order to get the maximumnumber of usages from such a bit, it is necessary that the original gauge di-.

ameter be regained during the reconditioning operation. Otherwise, the loss of'thisgaugediaineter will limit the use of the-bit insubs'equent 'drilling'coperations to those oifless diameter .where'such-reduced size bitrnay beuse'd.

is being-practi'ced-by othermethoda The method disclosed herein is intended to teach a new practice of resizing the bitto a diameter which, when-it issubsequently ground and regauged, will be approximately the same asthe original gaugediarneter before its initial An'important object of my invention has been theprovisi'on of a novel method of reconditioning dulled drill bits sothat they may subsequently be regauged'to agreaterdiameter than when dull.

Another object of my invention has been the provision of extremely simple,- easily operated,

durable shapingmeans for reconditioning dulled rock drill bits.

A further objeetnf my invention relates to the provision of tools-whereby the tooth of a dulled drill bit may be fulleredor swag-ed to a desired size without distorting the shape of" the tool or otherwise destroying its useful'nessy Still another object of theinvention has been the provision of an improved an'vilmeans for're ceiving' and holding the bit during the-reshaping operation, inwhich anvil the bit may be readily indexed to'prejsent ssequentially the various= wingsor cutting tjeeth on the face of the-bit tube-reshaped. I Y 5 A stillfurther object relates'to the provision of a bit tooth swaging bar havingfullering wings; which bar may be associated with averticall-y reciprocating means for" bringing it easily into an: improved bit sharpening-mechanism, whereby the Work may-be quickly performed with a mi'ni-' mum amount of manipulation and resultantly extremely low cost iorthe individual operations; Yet another obj 'eot of the invention is t'o' provide improvedmeans for positioning a drill bit,

for resharpening and for supporting it whilethe pressure of swagingmechanism i'sbeing applied for theresharpening operations which meansis simple of construction-andmaintenanceto effect low initial" and operating costs. I

Otherobj'eot's andadvantages ef the invention 'u iilfbe. more apparent during the course of: thefollowing description whereinl have'desorihed my novel method and illustrated a preferred .formi of; the. mechanism which I practice my method. It will'beunderstood'that while I have shown this mechanism having specifi'c' form and operation Ido not intend to'limit the scope ofmy invention beyond. the/definitions ofpthe sub; ioinedlolairnsb; a I J i r In-the, olrawin c 5 r V Figural is.aviewinielevation of adrill bit that has been dulledand inl conneetionavith which is 'ShOWll, in a niagnifiedportion ofthe d1'awi1'1g,.the original contour as well I as the 'resharpened: conjtoun thatresults froma the practice of my method in;-r eeonditioning such a drill bit, I

'Figure'Q-isnn. assembly" View of the swagezbar pearswhenpresented-for.reconditioning;

Figure 3 is an ienlargedi View of; a' swage bar of Figure 2 with portions? broken. away for: veni'ence oi illustratiomc i Figure 4 is a plan view of the swage bar as though looking at its bottom face,

Figure 5 is a perspective view of the anvil in which is positioned a drill bit to be reconditioned, and

Figure 6 is a side view of the anvil of Figure 5 with portions broken away for convenience of illustration. 7

Referring to the drawing, throughout which like reference characters indicate like parts, 10 designates a drill bit having a skirt l2 and a plurality of bit teeth l4, l6 and I8. The skirt I2 is drilled and threaded at 2B for attachment to the conventional drilling bar that is designed for use with the detachable bits of this nature. The

shank in his hand has little difliculty in holding the bit on the anvil.

Either the pressure downwardly of the swage bar may be slow and gradual or it may consist of a series of rapid blows such as are used in forging operations wherein the forging tool is moved mechanically with speed.

In practicing the' method the bit It is heated to a malleable state and so that it is somewhat annealed to remove to a degree temper in the metal. While the bit is in such a malleable state andhot it is affixed to the bit shank 38 and is 7 presented to the anvil so that the heel of a tooth usual water hole through the axial center of the describing a detachable drill bit it will be under- 7 stood that the practice of my method and the use of my mechanism is not limited to suchedevices. In the case of conventional steel wherein the drill teeth are formed on the end of a regular drill shank, the same may also be sharpened as is described herein.

In the'magnified portion of the drawing of Figure 1, I have indicated in dashed line and also labelled (1) the original contour of the bit;- in solid line, (2) the contour of the dulled bit; and finally in a second dashed line lying in a lower plane, (3) the resharpened contour of the bit after employing the method of my invention. Also indicated in the encircled magnified portion of the bit is the gauge loss between the original sharpening of the bit and its dulled diameter as well as the gauge diameter that is regained when the bit is gauged after the prac tics of my invention. I V

Upon a suitable base 24 I mount the anvil base plate 26 having thereon the anvil 28. The upper surface 30 of the anvil merges with the inner surface 32 of the bit saddle 34 which is curved and flared adjacent the saddle as indicated by the numeral 36. A drill bit, as I0, is positioned in the saddle so that the flared outer undercut portion of the drill bit wing, i.re., the heel of the bit tooth, rests on the curved portion 35 and also against the anvil face 30.

. In the case of detachable bits, a bit shank or handle 38 is inserted into the opening 30 of the bit and is used for manually. handling the bitand indexing it during the shaping operation on the anvil. i

, 'Upon a vertically movable reciprocable head 40 I mount the attaching plate'42 of the swage bar 44. Bar 44 may be substantially rectangular in cross-section and should be formed of durable stock for long use in teeth.

In a lower corner of the bar 44 I form a V- shaped groove 46 which has theflared fullering wings 48, 48 extending therefrom. The wings may be provided with teethas 49 "or under certain circumstances, may be perfectly smooth. The curved surfaces 48 are designed for vertical travel to contact the sloping sides of the bit teeth on either side of the cutting edge to be formed and to press the sides of the bit tooth toward each other to force the'metal downwardly and radially outward of the bit to increase the length of the material in which is formed the cutting edge of the tooth. The force of the swage bar is against the bit tooth primarily but it is transmitted to the anvil so that only slightly is itcarried on the bit shank. An operator grasping the shaping the drill bit or wing rests on the surface 30 in the path of the swagirig bar. The swage bar is lowered producing an opposed fullering action simultaneously on both sides of the metal forming the win and to swage it outwardly along the axis of the tooth to increase the overall diameter of the bit stock on its cutting face.

- The shaping of the remaining bit teeth is performed sequentially one tooth after another. To perform these operationsthe operator or tool handler merely indexes the bit, one-quarter or one-half of a turn in the case of a four-tooth bit, to present the next tooth to the fullering wings of the swage bar.

scribed, the bit is next presented to a conventional grinding tool .for smoothing the sloping faces of the bit teeth and also to a gauging grinder for accurately circumscribing the gauge diam eter of the bit. 7

In a subsequent operation the sharpened bit is accurately heated and retempered in the usual manner preferably by the liquid quench method to the desired degree of hardness. It has been found possible to sharpen, by the use of the mechanism shown herein and the method described in this specification, as many as six hundred or over hits a day, with but a single operator handling the mechanism and performing the operation.

In sharpening certain types of drill bits the metal of the drill bit is such that a smooth-faced fullering wing is not practical to use. In that case teeth 49 are provided on the two sides of the V-groove or curved faces of the wing so that they will grab or engage the hot metal of the bit tooth and draw it downward and outward along the axis of the cutter tooth to force the metal to the outer end thereof. n

It is an important result of this invention, as it will be notedfromthe foregoing specification, that my machine is especially. designed for the forming of the cutting surfaces of the rock drill bit at extremely high speed in an operation that can be efiicient and economical whether performed on a large scale or on arelatively small scale. a g

It will be further noted that by causing the swage bar with its fullering wings to travel at a relatively high speed in its reciprocating'motion and by heating the bit to a safe degree above the critical temperature prior to the forming operation, that the forming of the cutting surfaces of the bit is greatly facilitated, and that the wear of the cutters is thus greatly decreased.

It should-also be evident that by the exercise of only a reasonable degree of efficiency by an operator in handling the tool bar to which is attached the drill bit being sharpened that the forming process can be carried on. at a speed greatly increased over that of the conventional forging machine and over the method of sharpening drill bits.

When all of the teethof the bit have been reshaped as has been degrinding wheel the same time or at different times.

bodied in various other forms without departing from the spirit or scope of the claims.

While I have described a series of steps which constitute the preferred form of practicing my method, it will be apparent that the method may be carried out by varying the manner in which the steps are performed or by performing the steps in a varying order.

Also the apparatus described for carrying out my method is to. be understood to be exemplary and may be altered broadly as well as in specific detail to meet altered conditions. In certain cases it will be obvious that other apparatus may be substituted without departing from the principles of the invention.

With regard to the method described, the swage bar need not necessarily be moved but may remain fixed in which case the anvil and bit supported thereon will be moved toward and away from the immovable swage bar. On the other hand, the swage bar and anvil may both be moved toward and away from each other at In either of these cases the operation of the swage means upon a bit tooth is unchanged from the others, the principal point being to press the sides of a bit tooth that is properly supported towards each other whereby a motion is set up in the metal of the tooth and the cutting edge of the tooth is swaged radially outward from the axis of the hit.

As to the order in which each of the teeth is sharpened, they need not be forged one after the other around the bit. It can be seen that first one tooth may be swaged or forged, the bit be indexed 180 degrees to present the diametrically opposite tooth and the swaging step then performed thereupon. In such a schedule, the intermediate teeth would be later presented to the swaging means as desired and swaged as presented. Occasionally such a pattern may be suitable for the purposes of relieving strain or unnatural internal stresses, or for improving the grain structure in the metal of the bit.

An important point to be understood about my invention and more particularly about the relative movement between the swage means and the backing-up means is that the movement should be performed with force. Which of the elementsis to be moved depends upon the mechanism to be used to impart motion and to the circumstances surrounding the performance of'rny method. I 1

While the direction of movement has been described as vertical it will be obvious-that the 7 direction may be in any other plane so long as the pressure is applied to the sides of a'backedup tooth and they are pressed together.

Having thus described my invention, I claim:

1. The method of reconditioning a tooth of a Worn rock drill bit' which method comprises: supporting the heel of the bit toothto be sharpened, and striking the sides of the bit tooth toward each other but away from the axis of the bit while simultaneously wiping the metal of the tooth into a sharp cutting edge whereby the bit tooth is not only sharpened' but motion is set up to swage the tooth metal radially outward of the bit axis.

2. The method of reconditioning worn multitially present and support the remaining bit teeth and'producing cutting edges thereon as,

aforedescribed, and finally cutting the swaged bit to guage diameter.

3. The method of reconditioning worn multitoothed rock drill bits which comprises heating the bit to a forging temperature, positioning the bit so that the heel of a bit tooth is supported, and striking the sides of the bit'tooth toward each other but away from the axis of the bit while simultaneously wiping the metal of the tooth into a sharp cutting edge whereby the bit tooth is not only'sharpened but is swagedradial- 1y outward of the bit axis, next serially indexing the bit to sequentially present and support the remaining bit teeth and pressing as aforede-. scribed. I

4. The method of reconditioning a tooth of a dulled drill bit, which method comprises: supporting the heel of the, bit to be sharpened, and striking the sides of the bit tooth-toward each other rearward of the bit obliquely of the axis thereof 1 while simultaneously wiping the metal of the tooth toward the cutting edge-portion whereby a motion 'is set up in the tooth metal and the tooth is swaged radial of the bit axisand a new cuttingedge on the tooth'is simul taneously formed.

, RALPH noALHooN. 

